Production of play balls



P 3, 1936- D. F. TWISS ET AL 2,053,450

PRODUCTION PLAY BALLS Filed Nov. 8, 1934 INVENTORS Dou /11.: 27m NKTw/ss.

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Patented Sept. 8, 1936 UNITED STATES PATENT OFFICE 2,053,450 vPRODUCTION or PLAY BALLS Application November 8, 1934, Serial No.752,112 In Great Britain November 16, 1933 3 Claims.

This invention concerns improvements in or relating to the production ofplay balls, as for example tennis balls;

The object of the present invention is to produce play balls, forexample, tennis balls free from seams and other irregularities.

Heretofore, the inner cores or gas containers of play balls, such astennis balls, have usually beenproduced from shaped strips of compoundedrubber'mixings. The handling of such strips is, however, diificult anddefective joints with consequent leakage therefrom are a commonoccurrence,

In some'cases, the spherical container has been formed from twohemispherical cups of compounded rubber mixings, but this does notremove the risk of faulty joints.

Tennis balls and similarly inflated balls also suffer from leakage,which may be due to one or more of the three following causes:-

I. The highly compounded nature of the rubber compound of which thespherical gas container is formed.

2. Imperfect joints, accentuated in a large measure by the extremeflexing of the component parts. v

3. Ineffective sealing of the aperture through which gas is insertedwhen means such as hypodermic needle is employed for the purpose.

According to the present invention, the method for the production ofplay balls, for example, tennis balls comprises forming a relativelythin open hollow substantially spherical nucleus of elastic materialfrom a liquid composition thereof.bydeposition on a preferably sphericalformer, separating the substantially spherical elastic deposit from theformer, closing the aperture in the elastic deposit and thereaftercoating the thin elastic nucleus with rubber to the desired thickness.

The elastic material which forms the spherical nucleus is preferablymade of rubber.

The aperture in the thin elastic nucleus pro.-

duced can be closed, for example, either by tying or by applying a cappreferably one representing part of a sphere of the sameradius as thenucleus. The cap can be attached by means of rubber solution or latex.If the spherical former is supportedon, for instance, a thin wire, thenthe spherical nucleus can be removed by making a slit in the elasticmaterial, preferably on either side of the aperture formed by thesupporting wire and after removing thenucleus, sealing the slit with,for instance, rubber latex. Alterna tively, if desired, thesubstantially spherical nucleus.

former, hung for instance on a wire, can be made of material which canat will be rendered plastic or fluid.

The thin elastic spherical nucleus produced is then coated with rubberin any one or more of several ways, the spherical nucleus serving toprovide the desired configuration, The covering, for example, can beeffected by a dipping operation using a concentrated compounded rubberlatex, The cupping of each half of the spherical 10 nucleus may beeffected in several operations and the building-up of the necessarythickness may be facilitated and expedited by applying a coagulant tothe surface between two immersions in the latex. Other known methods ofaccelerating the formation of a layer of the necessary thickness canalso be employed.

Alternatively, the spherical nucleus of thin elastic material can becovered with compounded rubber by winding with unvulcanized, butvulcanizable, rubber tape whichmay be produced in any convenient way,for example, by calendering compounded rubber or by spreadingcoinpounded rubber solutions or latex. Thewinding is continued until anexternal layer of the desired thickness has been applied and the weightand dimensions of the ball are of the required magnitude.

Whichever procedure is adopted for coating the elastic nucleus withrubber, the article produced is subsequently vulcanized in a sphericalmould. In this way, a ball with a seamless wall is pro-= duced.

Inflating agents may be introduced into the spherical nucleus of thinelastic material before this is closed, or inflating agents may beintroduced at any stage subsequently by means of a hollow needle in wellknown manner. 'If a hollow needle is employed, it is desirable to applya suitable plug of soft rubber to the inside of the spherical nucleusbefore this is closed. It may 4 also be desirable to introduce agentsfor increasing the impermeability of the wall of the rubber ball to beproduced prior to the closing of the spherical nucleus; the constructionof the spherical nucleus and its possible transparency are featuresfacilitating the most efiective application of any lining material whichmay be spread uniformlyei .-r-.before or after the sealing of theWhe're' aqueous emulsions or dispersions of rubber are employed forproducing the spherical nucleus and/or for the subsequent coating of thesubstantially spherical nucleus of elastic material, the emulsions ordispersions can comprise'li'fi' used alone or in admixture with oneanother.

Any of the aforesaid dispersions may contain the usual known compoundingingredients and/ or may be in concentrated form.

Concentrates, such as are obtained in British Patents 290,313 and219,635, to which may be added any one or more of the usual compoundingingredients, may also be used.

The following are examples of the method for I the manufacture of playballs according to the present invention.

EXAMPLE 1 Calendered tape tennis balls A rubber bladder (of approximatecomposition rubber 92, sulphur 2, zinc oxide 1, mineral oil 4,accelerator 1) is made by dipping a spherical former not exceeding 2"diameter into a suitably compounded latex dispersion, or rubbersolution, and then vulcanizing the dried thin rubber deposit, afterwhich the neck portion is cut off. Blowing agents are then introducedbefore the rubber cap of similar curvature to the rubber depositconveniently perforated with a fine hole is cemented on with a rubber orlatex cement. which vulcanizes at ordinary temperatures without theapplication of any heat, as it is essential to prevent premature actionof the blowing agents. Shortly before the winding or building upoperation, the small pin hole in the rubber cap is sealed with a drop oflatex or rubber cement. By applying a small amount of latex dispersionto the base of the balloon its balance is made substantially perfect.The spherical bladder acts as a former on which the ball cover is builtup and becomes an integral part of the vulcanized ball. The exact mannerin which the spherical rubber bladder is made is of seconda yimportance, so long as it is of suitable size and strength.

A thin spherical rubber former is taken, made from a compounded latexdispersion; the complete thin sphere formed has a gross weight, 3.33grams of which' the blowing agents constitute ram. The thin rubberformer is then wound with calendered tape approximately 10 mms. wide and0.5 mm. thick, made from ordinary compounded milled rubber ofapproximate composition rubber 50, sulphur 3', clay 30, amorphous carbon9, zinc oxide 6, accelerator 2. The moderately adhesive tape is wound byhand under slight tension,-substantially after the manner of winding agolf ball, the tape being made to cover all parts of the former in auniform manner and so to build up an even thickness. The final weight ofthe ball before vulcanization amounts to 45.6 grams. The ball is thenimmediately placed in a ball mould of 2.28 internal diameter andvulcanized. After vulcanization, -the ball is covered with felt in theusual manner.

On cutting through the vulcanized rubber cover of a ball properly madefrom calendered tape, it is found that the tape'consolidates to acontinuous rubber mass and except on itsfree surface shows no evidenceof tape-winding construction. Further,- the physical tests on balls madeas indicated, have been found to be fully equal to balls made fromordinary V thick calendered sheets.

- Exmu: 2

Calendered tape tennis ball:

A ball is constructed as in Example 1, but the thin spherical rubberformer is covered with compounded rubber tape (of approximatecomposition rubber 80, sulphur 2, amorphous carbon 15, zinc oxide 2.accelerator 1) prepared from compounded latex by spreading on glass,drying and cutting into strips. vulcanization of the ball is eifected aspreviously.

Exmnn 3 Seamless later dipped ball A rubber bladder is used of typealready described, except that before the blowing agents are added, theinside of the bladder is coated with impermeable dope to increase theair-retaining qualities of the finished ball. The inside of the rubbersealing cap is also coated with impermeable dope, except where it is tobe cemented. Finally, the outside of the completed and sealed bladder iscoated all over with the dope, and allowed to stand for some time beforethe dipping operations begin. Any suitable dope may be used, which, forpreference is very flexible. The dope used consists of a mixture ofglyptal resin, gelatine and glycerine of the type described and claimedin copending application 713,376, filed February 28, 1934.

The special impermeable bladder is then dipped a total of 14 times in athick compounded latex dispersion and given a substantial coating ofcompounded rubber by latex-dipping, the dipping operations being carriedout so as to build up a uniform rubber deposit. Half the ball is dippedat each immersion. After every two dippings, the equatorial overlap iscompletely covered by the following two dips. The ballis rotated throughan angle of approximately 30 after every two dips, so that no twodippings ever occur over exactly the same area. After each dipping, the,deposited latex is coagulated by brief immersion in the vapour abovewarm acetic acid.

After the final immersion, there is produced a ball of very smoothappearance, showing only a slight dipping-mark around the circumference.The gross weight is 67.2 grams; the ball is then set aside fora few daysat room temperature to dry, when the weight becomes reduced to 51.1

grams.

vulcanization is eflected in the usual type of mould.

The various features of the invention are iilustrated in theaccompanying drawing in which Fig. 1 is a sectional-view of the nucleussealed before the application of the seamless wall; Fig. 2 is a viewillustrating the coating of the nucleus with the successive layers oflatex rubber; Fig. 3 is a view of the alternative method of winding tapeon the nucleus and Fig. 4 is a sectional view of the finished ball.

In the drawing the nucleus II has been slit at H to permit the removalof a former on which it has been formed. This slit II is closed by a capor catch I! which is cemented onto the outer wall of the nucleus. Theinner surface I! of the nucleus may have been coated with a coatingimpermeable to gases to render the'completed ball more nearly gas proof.A small pellet ll of gas generating material may be positioned in thenucleus before sealing it with the cap U2. The nucleus may then befilled with air or other gas to inflate it to the desired size. It isthen ready to receive and support the layers or coatings of rubber toform the seamless wall structure.

In the method of building up a wall structure by successively coatingthe nucleus with deposits of rubber from an aqueous dispersion, asillustrated in Fig. 2, the nucleus immersed in a bath l of aqueousrubber dispersion of suitable composition. The nucleus is preferablycoated for about one-half or a little over of its surface. With eachcoating, the coatings are alternated and overlapping, so that a completecoverage is obtained with each two clippings. These layers may bealternated in position to obtain uniformity.

In the method'of building up a wall structure by winding fiat compoundedrubber tape thereon as illustrated in Fig. 3, a tape I 6 oi? ribbon-likeor other suitable shape, is wrapped on the nucleus so as to obtain aneven distribution and is then compacted, the componued rubber merginginto one seamless mass as the rubber is vulcanized.

The resulting structure is as shown in *Fig. 4 in which a very thin wallof nucleus Ill remains on which has been built a seamless wall H. Thetwo merge on vulcanization into a single unitary structure. The innersurface l3 of the nucleus may have been coated with compositionimpermeable to gases and in this case will remain in the finished ballto improve its gas retaining qualities.

The seamless latex balls built on an impermeable bladder as describedhave superior air-retaining qualities, as compared with ordinary ballsmade from thick calendered sheet rubber in the standard manner.

Having now particularly described our invention, we claimv 1. The methodof forming seamless, hollow rubber balls of substantially uniform wallthickness, which comprises forming a nucleus consisting of a thin walledhollow spherical body of rubber having a wall thickness of only a smallfraction of the wall thickness of the ball to be formed, and thenbuilding up on the outside surface of said nucleus a seamless uniformlayer of rubber of a wall thickness of about ten or more times that ofsaid nucleus, and uniting said nucleus and said built up wall layer toan integral structure by vulcanization.

2. The method of claim 1 in which the wall is built on said nucleus bysuccessive deposits of unmasticated compounded rubber from an aqueousdispersion thereof.

3. The method of claim 1 in which, the wall is built up on said nucleusby winding unvulcanized rubber tape thereon until a wall is built and inwhich said windings are united into a seamless, uniform and integralstructure with said nucleus by vulcanization. v

DOUGLAS FRANK TWISS. WILLIAM MCCOWAN.

